#include <stdio.h>
#define N 71

int main()
{
    //freopen("test.txt", "r", stdin);
    int count, i, j;
    long long result[N] = {0};//注意类型大小

    result[0] = 0;
    result[1] = 1;
    result[2] = 2;
    for (i = 3; i < N; i++)
    {
        for (j = i - 1; j >= 1; j--)
            result[i] += result[j];//先保存起来，以后就不用每次都计算
        result[i]++;
    }

    while (scanf("%d", &count) != EOF)
    {
        printf("%lld\n", result[count]);
    }
    return 0;
}

/**************************************************************
Problem: 1389
User: lintingbin2009
Language: C
Result: Accepted
Time:0 ms
Memory:912 kb
 ****************************************************************/
